package main

import "encoding/json"
import "fmt"

func main() {
	a := struct{ Y string }{}
	b := struct{ X interface{} }{a}

	text := `{"X":{"Y":"zz"}}`
	if err := json.Unmarshal([]byte(text), &b); err != nil {
		fmt.Printf("json.Unmarshal: %v\n", err)
		return
	}
	fmt.Printf("%v\n", b)
}